scholarly journals Ceramide/Long-Chain Base Phosphate Rheostat in Saccharomyces cerevisiae: Regulation of Ceramide Synthesis by Elo3p and Cka2p

2003 ◽  
Vol 2 (2) ◽  
pp. 284-294 ◽  
Author(s):  
Scott D. Kobayashi ◽  
Marek M. Nagiec
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Protein Kinase ◽  
Wild Type ◽  
Α Subunit ◽  
Chain Base ◽  
Long Chain Base ◽  
Ceramide Synthesis ◽  
Long Chain ◽  
Ck2 Kinase

ABSTRACT Sphingolipid precursors, namely, ceramide and long-chain base phosphates (LCBPs), are important growth regulators with often opposite effects on mammalian cells. A set of enzymes that regulate the levels of these precursors, referred to as a ceramide/LCBP rheostat, is conserved in all eukaryotes. In order to gain further insight into the function of the rheostat in Saccharomyces cerevisiae, we searched for mutants that are synthetically lethal with a deletion of the LCB3 gene encoding LCBP phosphatase. In addition to acquiring expected mutants lacking the LCBP lyase, the screen revealed elo3 (sur4) mutants that were defective in fatty acid elongation and cka2 mutants lacking the α′ subunit of the protein kinase CK2 (casein kinase). Both mutations affected the in vivo activity of the acyl coenzyme A (acyl-CoA)-dependent and fumonisin B1-sensitive ceramide synthase (CS). The Elo3 protein is necessary for synthesis of C26-CoA, which in wild-type yeast is a source of C26 fatty acyls found in the ceramide moieties of all sphingolipids. In the in vitro assay, CS had a strong preference for acyl-CoAs containing longer acyl chains. This finding suggests that a block in the formation of C26-CoA in yeast may cause a reduction in the conversion of LCBs into ceramides and lead to an overaccumulation of LCBPs that is lethal in strains lacking the Lcb3 phosphatase. In fact, elo3 mutants were found to accumulate high levels of LCBs and LCBPs. The cka2 mutants, on the other hand, exhibited only 25 to 30% of the in vitro CS activity found in wild-type membranes, indicating that the α′ subunit of CK2 kinase is necessary for full activation of CS. The cka2 mutants also accumulated high levels of LCBs and had elevated levels of LCBPs. In addition, both the elo3 and cka2 mutants showed increased sensitivity to the CS inhibitors australifungin and fumonisin B1. Together, our data demonstrate that the levels of LCBPs in yeast are regulated by the rate of ceramide synthesis, which depends on CK2 kinase activity and is also strongly affected by the supply of C26-CoA. This is the first evidence indicating the involvement of protein kinase in the regulation of de novo sphingolipid synthesis in any organism.

scholarly journals The protein kinase Sch9 is a key regulator of sphingolipid metabolism in Saccharomyces cerevisiae

2014 ◽  
Vol 25 (1) ◽  
pp. 196-211 ◽  
Author(s):  
Erwin Swinnen ◽  
Tobias Wilms ◽  
Jolanta Idkowiak-Baldys ◽  
Bart Smets ◽  
Pepijn De Snijder ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Protein Kinase ◽  
Yeast Cells ◽  
Sphingolipid Metabolism ◽  
Long Chain Base ◽  
Aureobasidin A ◽  
Long Chain ◽  
Complex Sphingolipids

The Saccharomyces cerevisiae protein kinase Sch9 is an in vitro and in vivo effector of sphingolipid signaling. This study examines the link between Sch9 and sphingolipid metabolism in S. cerevisiae in vivo based on the observation that the sch9Δ mutant displays altered sensitivity to different inhibitors of sphingolipid metabolism, namely myriocin and aureobasidin A. Sphingolipid profiling indicates that sch9Δ cells have increased levels of long-chain bases and long-chain base-1 phosphates, decreased levels of several species of (phyto)ceramides, and altered ratios of complex sphingolipids. We show that the target of rapamycin complex 1–Sch9 signaling pathway functions to repress the expression of the ceramidase genes YDC1 and YPC1, thereby revealing, for the first time in yeast, a nutrient-dependent transcriptional mechanism involved in the regulation of sphingolipid metabolism. In addition, we establish that Sch9 affects the activity of the inositol phosphosphingolipid phospholipase C, Isc1, which is required for ceramide production by hydrolysis of complex sphingolipids. Given that sphingolipid metabolites play a crucial role in the regulation of stress tolerance and longevity of yeast cells, our data provide a model in which Sch9 regulates the latter phenotypes by acting not only as an effector but also as a regulator of sphingolipid metabolism.

scholarly journals Candida albicans sphingolipid C9-methyltransferase is involved in hyphal elongation

Microbiology ◽  
2010 ◽  
Vol 156 (4) ◽  
pp. 1234-1243 ◽  
Author(s):  
Takahiro Oura ◽  
Susumu Kajiwara
Keyword(s):  
Candida Albicans ◽  
Lipid Membrane ◽  
Hyphal Growth ◽  
Pathogenic Fungi ◽  
Wild Type ◽  
Membrane Structures ◽  
Pathogenic Yeast ◽  
Chain Base ◽  
Long Chain Base ◽  
Long Chain

C9-methylated glucosylceramide is a fungus-specific sphingolipid. This lipid is a major membrane component in the cell and is thought to play important roles in the growth and virulence of several fungal species. To investigate the importance of the methyl branch of the long-chain base in glucosylceramides in pathogenic fungi, we identified and characterized a sphingolipid C9-methyltransferase gene (MTS1, C9-MethylTransferase for Sphingolipid 1) in the pathogenic yeast Candida albicans. The mts1 disruptant lacked (E,E)-9-methylsphinga-4,8-dienine in its glucosylceramides and contained (E)-sphing-4-enine and (E,E)-sphinga-4,8-dienine. Reintroducing the MTS1 gene into the mts1 disruptant restored the synthesis of (E,E)-9-methylsphinga-4,8-dienine in the glucosylceramides. We also created a disruptant of the HSX11 gene, encoding glucosylceramide synthase, which catalyses the final step of glucosylceramide synthesis, in C. albicans and compared this mutant with the mts1 disruptant. The C. albicans mts1 and hsx11 disruptants both had a decreased hyphal growth rate compared to the wild-type strain. The hsx11 disruptant showed increased susceptibility to SDS and fluconazole, similar to a previously reported sld1 disruptant that contained only (E)-sphing-4-enine in its glucosylceramides, suggesting that these strains have defects in their cell membrane structures. In contrast, the mts1 disruptant grew similarly to wild-type in medium containing SDS or fluconazole. These results suggest that the C9-methyl group of a long-chain base in glucosylceramides plays an important role in the hyphal elongation of C. albicans independent of lipid membrane disruption.

Isolation of mutant Saccharomyces cerevisiae strains that survive without sphingolipids

1990 ◽  
Vol 10 (5) ◽  
pp. 2176-2181
Author(s):  
R C Dickson ◽  
G B Wells ◽  
A Schmidt ◽  
R L Lester
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Membrane Lipids ◽  
Molecular Genetic ◽  
Suppressor Gene ◽  
Molecular Genetic Analysis ◽  
Yeast Cells ◽  
Yeast Saccharomyces Cerevisiae ◽  
Chain Base ◽  
Long Chain Base ◽  
Long Chain

Sphingolipids comprise a large, widespread family of complex eucaryotic-membrane constituents of poorly defined function. The yeast Saccharomyces cerevisiae is particularly suited for studies of sphingolipid function because it contains a small number of sphingolipids and is amenable to molecular genetic analysis. Moreover, it is the only eucaryote in which mutants blocked in sphingolipid biosynthesis have been isolated. Beginning with a nonreverting sphingolipid-defective strain that requires the addition of the long-chain-base component of sphingolipids to the culture medium for growth, we isolated two strains carrying secondary, suppressor mutations that permit survival in the absence of exogenous long-chain base. Remarkably, the suppressor strains made little if any sphingolipid. A study of how the suppressor gene products compensate for the lack of sphingolipids may reveal the function(s) of these membrane lipids in yeast cells.

scholarly journals Sphingolipid long-chain-base auxotrophs of Saccharomyces cerevisiae: genetics, physiology, and a method for their selection.

1992 ◽  
Vol 174 (8) ◽  
pp. 2565-2574 ◽  
Author(s):  
W J Pinto ◽  
B Srinivasan ◽  
S Shepherd ◽  
A Schmidt ◽  
R C Dickson ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Chain Base ◽  
Long Chain Base ◽  
Long Chain

scholarly journals Isolation of mutant Saccharomyces cerevisiae strains that survive without sphingolipids.

1990 ◽  
Vol 10 (5) ◽  
pp. 2176-2181 ◽  
Author(s):  
R C Dickson ◽  
G B Wells ◽  
A Schmidt ◽  
R L Lester
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Membrane Lipids ◽  
Molecular Genetic ◽  
Suppressor Gene ◽  
Molecular Genetic Analysis ◽  
Yeast Cells ◽  
Yeast Saccharomyces Cerevisiae ◽  
Chain Base ◽  
Long Chain Base ◽  
Long Chain

Sphingolipids comprise a large, widespread family of complex eucaryotic-membrane constituents of poorly defined function. The yeast Saccharomyces cerevisiae is particularly suited for studies of sphingolipid function because it contains a small number of sphingolipids and is amenable to molecular genetic analysis. Moreover, it is the only eucaryote in which mutants blocked in sphingolipid biosynthesis have been isolated. Beginning with a nonreverting sphingolipid-defective strain that requires the addition of the long-chain-base component of sphingolipids to the culture medium for growth, we isolated two strains carrying secondary, suppressor mutations that permit survival in the absence of exogenous long-chain base. Remarkably, the suppressor strains made little if any sphingolipid. A study of how the suppressor gene products compensate for the lack of sphingolipids may reveal the function(s) of these membrane lipids in yeast cells.

scholarly journals TORC2-dependent protein kinase Ypk1 phosphorylates ceramide synthase to stimulate synthesis of complex sphingolipids

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Alexander Muir ◽  
Subramaniam Ramachandran ◽  
Françoise M Roelants ◽  
Garrett Timmons ◽  
Jeremy Thorner
Keyword(s):  
Protein Kinase ◽  
Specific Activity ◽  
Membrane Lipid ◽  
Ceramide Synthase ◽  
Dependent Protein Kinase ◽  
Chain Base ◽  
Long Chain Base ◽  
Dependent Protein ◽  
Abundance And Distribution ◽  
Long Chain

Plasma membrane lipid composition must be maintained during growth and under environmental insult. In yeast, signaling mediated by TOR Complex 2 (TORC2)-dependent protein kinase Ypk1 controls lipid abundance and distribution in response to membrane stress. Ypk1, among other actions, alleviates negative regulation of L-serine:palmitoyl-CoA acyltransferase, upregulating production of long-chain base precursors to sphingolipids. To explore other roles for TORC2-Ypk1 signaling in membrane homeostasis, we devised a three-tiered genome-wide screen to identify additional Ypk1 substrates, which pinpointed both catalytic subunits of the ceramide synthase complex. Ypk1-dependent phosphorylation of both proteins increased upon either sphingolipid depletion or heat shock and was important for cell survival. Sphingolipidomics, other biochemical measurements and genetic analysis demonstrated that these modifications of ceramide synthase increased its specific activity and stimulated channeling of long-chain base precursors into sphingolipid end-products. Control at this branch point also prevents accumulation of intermediates that could compromise cell growth by stimulating autophagy.

Sign in / Sign up

Export Citation Format

Share Document